Detergent composition and process

ABSTRACT

The invention disclosed is directed to a highly alkaline detergent composition having unexpectedly high tolerance with respect to hard water. The composition includes from about 10 to about 50 parts of an alkaline inorganic detergent component, from about 5 to about 30 parts of a tetra-alkali metal pyrophosphate component, from about 5 to about 30 parts of an alkali metal nitrilo triacetate component, from 0 to about 5 parts of a watersoluble nitrite component, and from 0 to about 5 parts of a lowfoaming surfactant. The composition is low-foaming in use dilutions and highly effective for machine dishwashing with less spotting and greater clarity of articles cleaned therewith. Also disclosed is a process for washing articles for cooking and eating using dilute aqueous solutions of the composition.

[ June 27, 1972 DETERGENT COMPOSITION AND PROCESS Inventors: Philip M.Sabatelli, Cincinnati, Ohio;

Charles A. Brungs, Fort Wright, Ky.

Assignee: Chemed Corporation, Cincinnati, Ohio Filed: July 22, 1970Appl. No.: 57,345

Related US. Application Data Continuation-impart of Ser. No. 680,966,Nov. 6, 1967, abandoned.

References Cited UNITED STATES PATENTS 2,671,717 3/1954 Ferguson ..41/42Drew et al. ..252/152 OTHER PUBLICATIONS Pfizer AminocarboxylicChelating Agents," Data Sheet No. 606,p. s (1963) Amino Acid ChelatingAgents in Detergent Soap & Chemical Specialties, (Sept, 1966) pp. 60,130, 133

Mechanical Dishwashing Compounds Lintner, A. E. Soap & ChemicalSpecialties, (July, 1967) pp. 42 & 89- 90 Primary Examiner-MayerWeinblatt Att0mey-Eugene M. Bond and Kenneth E. Prince [57] ABSTRACT Theinvention disclosed is directed to a highly alkaline detergentcomposition having unexpectedly high tolerance with respect to hardwater. The composition includes from about 10 to about 50 parts of analkaline inorganic detergent component, from about 5 to about 30 partsof a tetra-alkali metal pyrophosphate component, from about 5 to about30 parts of an alkali metal nitrilo triacetate component, from 0 toabout 5 parts of a water-soluble nitrite component, and from O to about5 parts of a low-foaming surfactant. The composition is low-foaming inuse dilutions and highly effective for machine dishwashing with lessspotting and greater clarity of articles cleaned therewith. Alsodisclosed is a process for washing articles for cooking and eating usingdilute aqueous solutions of the composition.

3 Claims, No Drawings DETERGENT COMPOSITION AND PROCESS This applicationis a continuation-in-part of US. Pat. Ser. No. 680,966, filed Nov. 6,1967 and now abandoned.

The present invention relates to a highly alkaline low-foaming detergentcomposition which more effectively removes food soils from glassware,dishes and the like with less spotting and greater clarity, and to awashing process using the composition. Unexpectedly, the compositionexhibits greater tolerance with respect to hard water than is to beexpected from the hardness tolerance exhibited by the several componentsof the composition taken alone.

institutional and household dishwashing machines have used stronglyalkaline solutions for washing dishware, glasses.

and other cooking and eating utensils. in cleaning processes for usingthese solutions ordinary tap water having varying degrees of hardness iscustomarily used to dilute the cleaning solution to use dilution and torinse the articles after a cleaning step. It is well known to thoseusing these cleaning solutions and processes that spotting by inorganicsalt residues and precipitates on the dishware and glassware is a majorproblem for appearance and other reasons. These precipitatesadditionally form lime scale and like deposits which interfere with theoperation of the washing equipment and necessitate frequent equipmentmaintenance. Although for softening hard water and other reasons sodiumtripolyphosphates and other condensed phosphates have been included inthese alkaline cleaning compositions, when used at elevated temperaturesthe otherwise desirable condensed phosphates rapidly hydrolyze toorthophosphates. These hydrolysis products often precipitate from thecleaning solutions resulting in increased article spotting andinterfering scale. Due to the highly alkaline conditions existing inthese cleaning solutions, organic compounds generally have not beenfound suitable to eliminate spotting for reasons such as lack ofadequate activity and interference with cleaning. Organic compoundswhich tend to inhibit spotting by inorganic salt residues have generallybeen found to function as foaming agents in com junction with thecleaning agents and food residues under the highly alkaline conditionsin the wash solution. As a practical matter, these organic compounds areinoperable in practice for machine dishwashing.

Detergent compositions containing nitrilo triacetates have beendisclosed in US Pat. No. 3,324,038 to Chaffee et a]. and Canadian Pat.No. 755,588 to Gedge. However, the compositions in both of these patentsinclude nitrilo triacetates as cleaning promoters for soaps and organicdetergents in substantially neutral systems where foaming is desirable.Prior to this invention, the utility of nitrilo triacetates in highlyalkaline, low foaming dishwashing compositions was not known.

It has now been found by practice of the present invention that there isprovided a superior machine dishwashing composition which moreeffectively removes food soils and residues from eating and cookingutensils such as dishes, glassware and the like while decreasingspotting and increasing clarity of the glassware and dishes relative tomost related compositions and methods of the prior art. Unexpectedly,the present composition exhibits greater tolerance with respect to waterhardness without formation of hard water scale than is to be expectedfrom the tolerance exhibited by the several components of thecomposition taken alone. This invention also provides a process for moreeffectively cleaning dishes, glassware, and other eating and cookingutensils with decreased spotting by salt residues.

Generally stated, practice of the present invention provides a detergentcomposition having improved use efficiency in hard water. In highlyalkaline use dilution, this detergent is characterized withsubstantially low foam-producing tendency and is highly suitable for usein machine dishwashing. The composition includes from about 10 to about50 parts by weight of an alkaline inorganic detergent component, fromabout 5 to about 30 parts by weight of a tetra-alkali metalpyrophosphate component, from about 5 to about 30 parts by a weight ofan alkali metal nitrilo triacetate component, from to about parts byweight of a water-soluble nitrite component and from 0 to about about 5parts by weight of a lowfoaming surfactant. This composition may beprepared in liquid form by including water in an amount of up to about99 parts by weight.

At from 0.05 to about 1 weight percent aqueous use dilution in waterhaving hardness up to about 25 grains per gallon, the presentcomposition exhibits substantial freedom from hard water precipiatates.This substantial freedom may be observed even though a weighted averagesequestering value of the composition based on the sequestering value ofthe components is substantially less than the hardness level of thediluting water used.

Broadly stated, the present process for washing dishes, glassware andother articles for eating and cooking includes applying to the articlesurfaces an aqueous solution of from about 0.05 to about 1 weightpercent, dry basis, of the present composition, and thereafter rinsingthe articles.

The alkaline detergent component of the present composition may beselected from alkali metal hydroxides and alkali metal silicates.Suitable alkali metal hydroxides include sodium hydroxide, potassiumhydroxide and mixtures thereof. Suitable alkali metal silicates includesodium silicate, potassium silicate and mixtures thereof. A preferredsilicate is sodium meta-silicate. The alkaline detergent component maybe included in an operable amount of from about 10 to about 50 partsbyweight, and preferably from about 10 to about 20 parts by weight. Milderalkaline materials such as sodium and potassium carbonates and sodiumand potassium orthophosphates may be substituted to a limited extent forsome of the alkaline detergent. For example, 0 to about 20 weightpercent of the alkaline detergent may be replaced with sodium andpotassium orthophosphates, sodium and potassium carbonates and mixturesof these materials. Preferably, sodium hydroxide is used as the alkalinedetergent component.

The tetra-alkali metal pyrophosphate component of this composition maybe any alkali metal pyrophosphate such as tetra-sodium andtetra-potassium pyrophosphate. A preferred pyrophosphate istetrapotassium pyrophosphate. Significantly,

other condensed phosphates, such as sodium tripolyphosphate v and thelike are not required in the composition. The pyrophosphate componentmay be included in an operable amount of from about 5 to about 30 partsby weight and preferably from about 10 to about 30 parts by weight.

The alkali metal nitrilo triacetate component of this composition may beselected from the sodium and potassium salts. The tri-alkali salts aregenerally preferred. A preferred triacetate is trisodium nitrilotriacetate. The triacetate may be included in an operable amount fromabout 5 to about 30 parts by weight, and preferably from about 5 toabout 20 parts by weight.

The optional nitrite component of this composition may be anywater-soluble nitrite salt such as alkali metal nitrites includingsodium, potassium, and lithium nitrite; alkaline earth metal nitritesincluding calcium and magnesium nitrite; ammonium nitrite and the like.A preferred nitrite is sodium nitrite. Where used, the optional nitritecomponent is principally included for increased suitability of steel andthe like for containerization and extended storage of the presentcomposition. The nitrite component may optionally be included in anamount from 0 to about 5 parts by weight, although an amount from about0.1 to about 0.5 part by weight is generally suitable for extendedstorage in steel drums.

The optional surfactant component may be almost any water-solublesurfactant having low foam-producing tendency in highly alkaline aqueoussolutions. The surfactant component may be included in an amount from 0to about 5 parts by weight.

The present composition may be stored and used as either a substantiallydry mixture of the various components or a concentrated solution ofthese components with from about 20 to about weight percent water.Preferably, liquid concentrates of this dishwashing composition includefrom about 40 to about 80 weight percent water.

A preferred low foaming detergent composition of this invention formachine dishwashing includes from about to about 20 parts by weight ofpotassium hydroxide, from about to about parts by weight oftetrapotassium pyrophosphate, from about 5 to about parts by weight oftrisodium nitrilo triacetate, and from about 20 to about 80 parts byweight of water. This preferred composition may further include fromabout 0.1 to about 0.5 part by weight of sodium nitrite, if desired.

The present process includes applying to surfaces of articles to becleaned an aqueous solution including from about 0.05 to about 1 weightpercent and preferably from about 0.05 to about 0.5 weight percent ofthe machine dishwashing composition. The composition may be applied at atemperature of from about 140F to about 200F and preferably from aboutl40F to about 160F. Although application of the aqueous detergentsolution to the surfaces may be effected by any suitable means, theprocess is more highly effective when used with spray washing equipmentof the type used typically for cleaning utensils for cooking and eating.Highly effective cleaning with low foaming is obtained in institutionaland household dishwashing machines with this composition. In the finalstep of the cleaning process, the cleaned surfaces are preferably rinsedwith water.

The improved alkaline dishwashing composition of this invention ishighly effective in use for removing food soils and residues fromdishes, glassware, and other cooking and eating utensils in dishwashingmachines. Not only are the food residues more effectively removed withthis composition, but the cleaned dishes and glassware exhibit lessspotting and greater clarity than are typically observed for prior artcleaning compositions.

This invention is further illustrated by the following nonlimitingexamples. In this description, including the examples which follow, allparts and percentages given are by weight unless otherwise specified.

EXAMPLE 1 A mixed condensed phosphate type machine dishwashingcomposition was prepared by admixing about 15 parts of potassiumhydroxide, about 15 parts of tetrapotassium pyrophosphate, about 15parts of sodium tripolyphosphate, and about 0.3 part of sodium nitritewith about 54.7 parts of water. The concentrated liquid composition thusprepared was then diluted with a quantity of Cincinnati tap water havinga hardness of 192.5 ppm. to form a control wash solution including a 0.3percent of the concentrate.

EXAMPLE 2 A 0.3 wash solution was prepared by the procedure of example 1except the 15 parts of sodium tripolyphosphate were substituted by 15parts of sodium nitrilo triacetate.

EXAMPLE 3 The control solution of example 1 and the wash solution ofexample 2 were tested using a Hobart A.M. dishwashing machine having a48 second wash cycle and a 12 second rinse cycle. The test articles were22 squares of plate glass 4 inches on each edge which were soiled withone gram of a soil containing 50 parts peanut butter, 25 partshydrogenated vegetable oil, and 25 parts butter. No rinse additive wasused. The wash solutions had a temperature of 150F in the wash section.The rinse water was 192.5 ppm. hardness Cincinnati tap water used at180F.

In a first test 10 soiled glass plates were run through 8 cycles in themachine with a drying period of 15 minutes allowed between cycles. Thetest plates washed using the nitrilo triacetate including wash solutionof example 2 were substantially clearer and less streaked relative tothe glass plates washed using the tripolyphosphate including controlsolution of example 1. Relative to the control-washed plates, the plateswashed using the solution including nitrilo triacetate were notablybrighter, and substantially fewer spots appeared thereon. The results ofcounting the number of spots appearing on both sides of 1 square inch ofthe center of each plate are shown below:

Inspection of the dishwashing machine before and after using thesesolutions showed that considerably less hard water scale was depositedthereon using the nitrilo triacetate including solution than was notedwhen the control solution was used.

A second washing test was performed using test plates nos. 21 and 22 andthe washing procedure of the first test, except the number of cycles wasreduced from 8 cycles to 1 cycle. The plate used to test the nitrilotriacetate including wash solution exhibited 14 spots whereas 78 spotsappeared on the control-washed plate. This test shows that when usingless washing time, such as is highly desirable in practice, even greatersuperiority of the nitrilo triacetate including solution is exhibitedthan was noted in the first test.

EXAMPLE 4 Samples of the concentrated liquid compositions of examples land 2 are diluted to 0.3 percent aqueous solutions having 5, l5, and 25grains of hardness per gallon. The hardening agents are calcium acetateand magnesium sulfate. These dilute solutions are heated to F and pouredinto 27 X 275 glass cylinders and allowed to stand for 24 hours. At theend of this period the tripolyphosphate including solution having 5grains hardness has a clear appearance and substantially no precipitate.However, the cylinders filled with the 15 grain and 25 grain hardnesstripolyphosphate including solutions are found to have substantialdepths of precipitates. These results are as expected in view of theweighted average chelating value of the tripolyphosphate containingsolution which is calculated to be about 7 grains per gallon. The 7grain chelating value follows from individual chelating values observedfor the tripolyphosphate and pyrophosphate at the dilution, pH andtemperature used for precipitate tests.

After 24 hours standing all the 5, l5 and 25 grain hardness samplesprepared using the nitrilo triacetate including solutions are observedto be substantially clear and free from precipitates. Although noprecipitate is expected for the 5 grain hardness sample, the freedomfrom precipitate formation is unexpected for the 15 and 25 grain samplesin view of the approximate l 1 grain weighted average chelating value ofthe nitrilo triacetate including solutions. The l 1 grain chelatingvalue follows from a calculation procedure and observa tions similar tothose used for the tripolyphosphate including solutions.

EXAMPLES 5 and 6 The procedures of Example 3 and 4 are repeated exceptno nitrite is used. The results are substantially the same as theresults noted in Examples 3 and 4.

EXAMPLE 7 A mixed condensed phosphate type machine dishwashingcomposition was prepared by admixing about 31 parts of liquid causticpotash, about 20 parts of 60 percent liquid tetrapotassiumpyrophosphate, and about 13 parts sodium tripolyphosphate with about 36parts of water. Samples of the concentrated liquid composition thusprepared were then diluted to 0.3 percent solutions using 5 samples ofwater having hardness of 0, 5, 10, 15 and 20 grains per gallon expressedin equivalent amounts of calcium carbonate. The hard water samples wereprepared using calcium acetate and magnesium sulfate hardening agents.

The dilute solutions of this mixed condensed phosphate includingcomposition had a weighted average sequestering ability of 6.8 grainsper gallon (i.e., 116.1 milligrams of calcium carbonate per liter) atthe pH of the 0.3 percent solutions (i.e., about 12 pH). Thesequestering value was calculated from Mehltretter Test sequesteringvalue observations at 12 pH of 246 milligrams of calcium carbonate pergram of the tripolyphosphate component and 33.6 milligrams of calciumcarbonate per gram of the liquid pyrophosphate component.

EXAMPLE 8 A Mehltretter Test observation of 370 milligrams per gramsequestering value was made for trisodium nitrilo triacetate monohydrateat 12 pH. Using this value a concentrated composition having acalculated weighted average sequestering ability of 6.8 grains pergallon at 0.3 percent aqueous solution was formulated. This concentratewas prepared by admixing about 31 parts of liquid caustic potash andabout 10.5 parts of trisodium nitrilo triacetate monohydrate with about58.5 parts of water. It is to be noted that at the same use dilutionthis concentrate had the same calculated sequestering value as theconcentrate of example 7, and likewise had a pH of about 12. Thisconcentrate was then diluted to 0.3 percent solutions using theprocedure of example 7 to form 5 dilute samples having 0, 5, l0, l5 and20 grains per gallon hardness.

EXAMPLE 9 The dilute solutions of examples 7 and 8 were heated to 150Fand poured into 27 X 275 mm glass cylinders and allowed to stand for 24hours. No precipitate was observed in the dilute solutions containingmixed phosphates at 0, 5, and 10 grains of hardness. The and grainhardness solutions were observed to have deep accumulations of limescale precipitate measuring 22 mm and 38 mm in depth, respectively.

In contrast to the phosphate-containing solutions, no precipitate wasobserved at any of the hardness levels from 0 to 20 grains for thetriacetate containing solutions. No floc was observed for any of thesetriacetate solutions, not even at the i5 and 20 grain hardness levels.These results are unexpected in view of the mere 6.8 grain sequesteringvalue of the triacetate containing solution.

This example shows that even at the same sequestering value, the nitrilotriacetate is superior to mixed phosphates in water softening ability inhighly alkaline, low-foaming detergent compositions at a typical usetemperature for machine dishwashing. It is also noted that the nitrilotriacetate prevents formation of lime scale in solutions of hardnessconsiderably in excess of the hardness at which scale formation is to beexpected.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that various modifications may be madetherein without departing from the spirit or scope of the presentinvention.

What is claimed is:

1. A process for cleaning an article fouled with food or cooking soilwhich comprises, applying to the article an aqueous solution having atemperature of from about MDT to about 200F, said aqueous solutioncontaining from about 0.05 to about 1 weight percent dry basis of alow-foaming dishwashing composition consisting essentially of a. fromabout 10 to about 50 parts by weight of an alkali metal h droxide, b.from 21 out 5 to about 30 parts by weight of an alkali metalpyrophosphate,

c. from about 5 to about 30 parts by weight of an alkali metalnitrilotriacetate,

d. from 0 to about 5 parts by weight of a water-soluble nitrite, and

e. from 0 to about 99 parts by weight of water and thereafter rinsingthe article.

2. The process of claim 1 wherein said composition consists essentiallyof:

a. from about 10 to about 20 parts by weight of an alkali metalhydroxide,

b. from about 10 to about 30 parts by weight of an alkali metalpyrophosphate,

c. from about 5 to about 20 parts by weight of an alkali metalnitrilotriacetate,

d. from 0 to about 0.5 parts by weight of a water-soluble nitrite,

e. from about 20 to about parts by weight of water.

3. The process of claim 1 wherein said composition consists essentiallyof: T

a. from about 10 to about hydroxide,

b. from about 10 to about 30 parts by weight of tetrapotassiumpyrophosphate,

c. from about 5 to about 20 parts by weight of sodium nitrilotriacetate,

d. from O to about 0.5 part by weight of sodium nitrite,

e. from about 20 to about 80 parts by weight water.

20 parts by weight of potassium

2. The process of claim 1 wherein said composition consists essentiallyof: a. from about 10 to about 20 parts by weight of an alkali metalhydroxide, b. from about 10 to about 30 parts by weight of an alkalimetal pyrophosphate, c. from about 5 to about 20 parts by weight of analkali metal nitrilotriacetate, d. from 0 to about 0.5 parts by weightof a water-soluble nitrite, e. from about 20 to about 80 parts by weightof water.
 3. The process of claim 1 wherein said composition consistsessentially of: a. from about 10 to about 20 parts by weight ofpotassium hydroxide, b. from about 10 to about 30 parts by weight oftetrapotassium pyrophosphate, c. from about 5 to about 20 parts byweight of sodium nitrilo triacetate, d. from 0 to about 0.5 part byweight of sodium nitrite, e. from about 20 to about 80 parts by weightwater.